1. Field of the Invention
The invention relates to a ball emitting apparatus and more particularly to a tennis practicing machine.
2. Description of the Prior Art
It is known to provide a tennis practicing machine of the type shown in FIG. 1 of the drawings. A ball retrieval net 1 is positioned to collect balls which are hit at it by a student practicing tennis. The net 1 has a substantially vertical curtain 3f suspended from a horizontal crossbar 2. The vertical portion 3f terminates short of a base netting 3b which is slanted in a funnel-like fashion towards the aperture 6 of the machine or apparatus 5. The net 1 also has a back portion 3e and side portions 3d and 3g. A front apron 3a is also provided tied to a lower crossbar 2f.
The upper horizontal bar 2 is supported by two legs 2c and 2d or 2a and 2b at respective ends of the bar 2. Slant supporting bars 2h and 2g are also provided from respective legs 2d and 2c.
In front of the aperture 6 a front netting 3a is arranged above which balls entering the net 1 must pass.
As a ball is hit by a tennis player into the netting 1, it falls onto the netting floor portion 3b and is funneled into the tube 7 of machine 5 at aperture 6.
A window 4 is provided in netting portion 3a through which balls are emitted from the machine 5.
Consequently, with the practicing machine described, a tennis player hits the balls projected from machine 5 into the netting 1 where they are "recycled" back into machine 5 for repetitive emission.
With the system described above, a tennis emitting machine 5 such as shown in FIG. 2 preferably has an auxiliary power switch 20 so as to allow an operator to initiate operation of the system from a distance. A window 10 is provided in the apparatus 5 through which the balls 9 are emitted.
As shown in FIG. 3, the prior art machine has a drive motor 16 connecting through gearing 15 to a rotating arm 13 on a shaft 14. A spring 17 stores energy as the arm 13 rotates until the arm 13 reaches a predetermined point during rotation in the direction a at which time the arm 13 suddenly rapidly accelerates so as to project a ball 9 in well-known fashion. A guide 12 guides the tennis balls 9 to the point of projection. A slip clutch of well known design permits the arm 13 to rotate forward free of gear 15 when the spring 17 rapidly rotates arm 13.
A base 18 is mounted on a chassis 11 to provide a mounting wall for the rotating arm 13.
Rotating arm 13 has a longer portion 13b opposite the peg 13a so that said longer portion will strike the ball a half rotation after peg 13a passes the ball.
With the above-described system, there is the disadvantage that if the machine is shut off, the arm 13 may come to rest near its trigger point for ball emission. In other words, the spring 17 will be stretched to the point of maximum energy storage. If the tennis ball emission machine 5 were accidentally jostled, it is possible that a ball can be accidentally emitted and strike an unwary player.
There is also the disadvantage that when the machine is set in operation that a ball will be emitted before the tennis player is ready for hitting.
An additional disadvantage of the known system is that when the machine is plugged into a power main having a power line frequency of 50 Hz rather than 60 Hz, that the machine will operate over an undesirably slower time period.